Bi-static radar is useful for various purposes, including improved probability of detection, formation of a larger antenna aperture through the combination of signals received from multiple radar-transceiver, etc. An important motivation for larger antenna aperture, and perhaps the primary motivation for coherent bi-static radar, is much improved angle capability (accuracy and discrimination). Coherent radar-transceiver operation will provide improved performance for bi-static radar compared to those operating with independent VCOs. A known method to make multiple homodyne receivers coherent is to distribute the Local Oscillator signal (LO) to each receiver for down conversion. However, at millimeter wave-length frequencies, this can be expensive or impractical when the receivers have significant separation. A known method for VCO control is a Fractional N PLL, in which the VCO frequency is divided and then compared to a reference oscillator. A known technique for generating frequency modulation of the VCO is for the divider in the Fractional N PLL to be varied over time. One example is a linear FM sweep. It is common that the reference oscillator for the Fractional N PLL is also used as a clock source to control frequency modulation and data acquisition with an ADC. Any difference in the time that the FM sweep is started in two sensors will appear as a range delay. This can be calibrated out through processing of received signals.